What shaped plunger do I need?

[Easipeelerie]

I’ve bought various different plungers to unblock a toilet but they don’t work. I can’t make a seal partly because our toilets are kind of arch shaped? Are there plungers that fit that shape?

There's videos on YouTube where they seal the whole toilet bowl with cling film, put the lid down and then flush.
Not tried it, but maybe worth googling.